1. Field of the Invention
The invention relates in general to a frequency offset estimation method and associated apparatus for a multi-carrier communication system, and more particularly, to a frequency offset estimation method and associated apparatus for Digital Video Broadcasting Terrestrial (DVB-T) and Integrated Services Digital Broadcasting (ISDB-T) systems.
2. Description of the Related Art
A multi-carrier communication system based on the orthogonal frequency division multiplexing (OFDM) technology is applicable to DVB-T and ISDB-T systems. In general, the OFDM technology is extremely sensitive to an offset in a carrier frequency. Due to mismatch between oscillators of a transmitter and a receiver, the frequency offset needs to be first calculated and compensated at the receiver in order to receive and correctly decode data signals.
In a DVB-T system, a continual pilot (CP) signal is utilized for estimating the frequency offset. For example, the U.S. Pat. No. 8,149,962 discloses a method for estimating a frequency shift. In certain ISDB-systems, due to an insufficient number or the lack of CP signals, the frequency offset cannot be accordingly estimated. Thus, in an ISDB-T system, the frequency offset is estimated by using a transmission and multiplexing configuration control (TMCC) signal or an auxiliary channel (AC) signal. For example, the U.S. Pat. No. 8,064,553 discloses a method for coarse frequency offset estimation in an ISDB-T receiver.
It is known from the above that, the CP signal in a DVT-T system is a specific, time-invariant real number appearing at a fixed frequency, and the TMCC signal and the AC signal in an ISDB-T system are information-carrying, time-variant real numbers appearing a fixed frequency.
Thus, the method for estimating the frequency shift as disclosed by the U.S. Pat. No. 8,149,962, involving only the CP signal for estimating the frequency shift, is applicable to a DVB-T system but not to an ISDB-T system.
Further, the method for estimating the frequency offset as disclosed by the U.S. Pat. No. 8,064,553, involving only the TMCC signal and the AC signal for determining the frequency offset, is applicable to an ISDB-T system but not to a DVB-T system.